Toxic chemicals in fish and wildlife at the Big Bend National Park, Texas
Irwin RJ. 1989. Toxic chemicals in fish and wildlife at the Big Bend National Park, Texas. Contaminants Report. National Park Service
Residues of up to 67 chemical contaminants were measured in 53 samples of fish, turtles, insects, birds, and sediments from two Rio Grande sites. A total of 35 samples were analyzed for organochlorines and PCBs, 18 samples were analyzed for heavy metals, and 8 samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons. Except for DDT, DDD, and DDE, all samples were notably free of significant contamination by organochlorine contaminants. Mercury was only slightly elevated in most fish and wildlife samples and is not known to be an important cause of eggshell thinning in peregrines. Some of the levels of DDE, PAHs, and combined heavy metals in fish and wildlife tissues were sufficiently elevated to cause concern for predatory species of fish and wildlife. DDE was found in concentrations exceeding predator concern levels in several small bird samples. DDE was also detected in a Rio Grande aquatic insect sample. Therefore, aquatic insects may be one source of DDE being biomagnified into the peregrine falcon food chain via insectivorous birds. In this way, the Rio Grande may be serving as one potentially harmful source of DDE available to the peregrine falcons in Big Bend National Park. The Rio Conchos and other Mexican sources are suspected as the main source of DDE in the Rio Grande at Big Bend National Park. Continued sale of DDT in Mexico, its use in farming upstream in Mexico, and the presence of a pesticide facility upstream on the Rio Conchos (near Delicias, Mexico) have all been suggested as potential sources of DDT and its breakdown product, DDE, in the Rio Grande. More field investigations in Mexico in the Rio Conchos drainage upstream of its confluence with the Rio Grande would be necessary to more precisely identify the sources of DDE entering the Rio Grande from the Rio Conchos. Identifying and eliminating upstream sources of DDT/DDE and PAHs would probably be more helpful to the peregrine falcons and other fish and wildlife of the Big Bend area than carrying out additional field contaminant studies in the Rio Grande at Big Bend National Park at this time
- Type
- Published Report
- Authors
- Irwin, Roy
- Date of Issue
- 1989-03
- Publisher
- National Park Service
- Units
- BIBE , WRD
- Keywords
- aliphatic hydrocarbons, Animal Studies, Birds (Aves), Bony Fishes (Osteichthyes), Chlorinated Hydrocarbons (PCB, Clemson, DDE, HCB), Heavy Metals, Insects (Insecta), Organochlorines, Peregrine Falcon (Falco peregrinus) - Falconidae, Pesticides, Polycyclic Aromatic Hydrocarbons (PAHs), Rio Grande (River), Soils, Toxins, Turtles & Tortoises (Testudines), Water Quality, WRBIB